Compression test results?

Gary WA

Gary WA

Well-known member
Warm engine, getting blowby out fill tube, #1-60/#2-60/#3-50/#4-55:with a squirt of oil:#1-70/#2-65/#3-65/#4-65.Changed out tube a few times,Could rear main drain tube be plugged? any other Ideas?:confused:
 
blowby is a byproduct of compression getting below the rings into the crankcase. the pressure built up in the crankcase is then exhausted out of the breather. the main causes for blowby are pistons, rings, or cylinder wall problems. on a newly rebuilt engine sometimes minimal blowby is normal until the rings seat. i hope that motor on your engine stand is not the one with blowby
 
Last edited:
Did you install each ring in each bore to check end gap before you went ahead to install them on the pistons? I pulled an engine apart recently that had the wrong rings in it, they had about .040 end gap, you should only have about .012. If you just went ahead and took them out of the box and put them on the slugs, then maybe they were boxed wrong. Just a thought. Unfortuneatly, I don't think there is much you can do to get more compression without taking the pistons out to confirm everything.
 
Gary WA said:
Any other Ideas????? Before I start Dismantling!!!!
Click to expand...
Gary,

Is blowby the only issue or is it smoking alot out the tail pipe? If power is OK for your use and blowby is the only problem then have you checked service bulletin page 454? Ford had problems with blowby in 1930 when the engines were low mileage. SB 454 and 358 show pictures of the three different baffle designs. SB Page 358 shows the two older version breather tubes.

I would buy a new tube (or check out any old ones that you may try to see if they are made to the new specs ... that is the angle and arrangement of the internal baffles). Also ask supplier if it meets the standards of SB 454. Maybe not all Repro tubes are manufactured to these specs. Some one could be making repros to the older specs.

Another option is to find a Model B breather tube ... they have improved baffles and a larger tube and do a better job of returning oil droplets and vapor to the crankcase.
 
Last edited:
No smoke out tailpipe.All the tubes I have are older ones but will check them out. Going to do the Bag trick and see if it flutters or has air over the breather tube. Or pull the pistons and pan to check things thanks for info.
 
Gary,
I guess it depends on how much of a blow by problem you have, I have some blow by on my A model also, i put on a road tube from snyder's about 500 miles ago and it seem's to take care of the problem in my case. just a sug.
 
You must log in or register to reply here.
Back
Top